The present invention relates generally to sonic examination of workpieces and other objects, and particularly to an automated system that maintains parallel relationship between the working face of a sound transducer and the planar surface of a workpiece.
In using sonic and ultrasonic energy to examine a workpiece for discontinuities that may be in the workpiece, it is desirable to maintain the face of the transducer that directs the sound energy into the workpiece in parallel relationship with the workpiece. In this manner the transducer receives a amaximum amount of energy reflected from the workpiece in the examination process. The receipt of a maximum signal from the workpiece under examination insures a correct reading of the internal structure and integrity of the workpiece. It can be appreciated that if the transducer and associated examining circuitry are not receiving the best possible signal from the workpiece, the results of the examination are compromised.
In U.S. Pat. No. 4,043,185 to Siebert, ultrasonic examining heads are maintained parallel with a plate or sheet being examined by physically disposing the heads on and in physical contact with the sheet, using low friction pads in contact with the sheet. A mechanically pivotal linkage structure supports the heads. Such means have certain disadvantages in that the readings provided by the heads may be affected by uneven surface conditions of the sheet. Similarly, movement of the heads and linkage, after a period of time and use, might cause wear at the linkage joints such that erroneous readings (again) might be the result. Further, it is preferred that a water path be provided and maintained between the examining heads and the surface of the object under examination, the water path providing a mechanism for coupling the sound energy into the object under examination that is not affected by surface conditions of the workpiece or object. And lastly, any physical contact with the workpiece offers the opportunity for scratching or otherwise damaging or marking the workpiece surface.